Painfully well-observed, malevolently funny and beautifully acted, the first half of David Eldridge's "In Basildon" rises to a cliffhanger about the reading of a will.

“Well, we’ll have to see, won’t we doll?” threatens hard-as-nails Doreen (Linda Bassett). “Yes doll, we will,” returns her sister Maureen (Ruth Sheen). Painfully well-observed, malevolently funny and beautifully acted, the first half of David Eldridge’s “In Basildon” rises to a cliffhanger about the reading of a will. Sadly, in the second half it’s not just the contents of that will that disappoint. Even direction as good as Dominic Cooke’s cannot disguise the slide from grippingly implicit class politics into the unconvincingly explicit.

Families and their misfortunes are hardly new topics for drama, especially when set around a funeral. The difference here is location. There’s a saleable house at the play’s heart but we’re not on a Chekhovian estate, we’re in Basildon, a town in what used to be the predominantly working-class county of Essex bordering London’s East End.

A byword for vulgar in middle-class media parlance, Essex is famous for being peopled by families moved there from bombed-out slum dwellings after World War II. It’s also the place that symbolized the winning 1980s Conservative party vote. It’s that collision that Essex-born Eldridge anatomizes.

The political legacy is, for the first half, obscured by the entertainingly inappropriate infighting of the family gathered around the deathbed of 60-year-old Len (Phil Cornwell).

Tensions are already running high because everyone is after his house, which he long ago promised to Doreen’s feckless son Barry (Lee Ross) and his wife Jackie (Debbie Chazen). To everyone’s annoyance but the audience’s amusement, next-door Pam (poised Wendy Nottingham) is lending a hand and Len’s best friend Ken (self-satisfied Peter Wight), a self-made businessman, is cheerfully riling everyone.

Doreen’s nose is put severely out of joint by the arrival of younger sister Maureen, to whom she has not spoken in 20 years. Wielding vicious comic civility, hilarious double-entendres, fouled-mouthed put-downs — these two launch the word “darling” at each like harpoons — and expertly controlled silences, Eldridge wins big laughs and wide-ranging sympathies for the straitened circumstances of almost all his characters.

There’s a whiff of “August: Osage County” about this family-reunion-from-hell scenario, but where that play was built on the unearthing of secrets, Eldridge focuses on the conflicting class politics that define the lives of his characters. This is brought to the fore metaphorically by the potential inheritance, and literally via Tom (Max Bennett), the posh, wannabe playwright who is the steady boyfriend of Shelley (Jade Williams), the only family member ever to go to university.

It’s Eldridge’s judgmental handling of this character that tips the proceedings from theatre to treatise. Whereas Shelley’s hatred of her background is sharply argued, Tom is too obviously an “outsider” and a caricature.

The laughs at his expense are woefully easy, and although Eldridge gives him the excuse of being fairly drunk, Tom’s pompous opinions and attacks on everyone’s values are so overwhelmingly insensitive and naive that they make no sense coming from a 27-year-old teacher. But they’re necessary, alas, to open up the debates that unravel and flatten the second half.

The last scene is an unexpected flashback showing how money and loyalties caused the rift that wrecked the family, but the revelation doesn’t deepen what we’ve already witnessed. The scene sums up the play: It’s appropriate to Eldridge’s thematic purpose but it fails to drive drama.

In Basildon

Royal Court Theater, London; 370 seats; £28 $44 top

Production

A Royal Court Theater presentation of a play in two acts by David Eldridge. Directed by Dominic Cooke.